Tuning Motronic to burn very clean for MOT / NCT without cats

[s2_wot]

Another tuning question guys.

In Ireland we have the NCT which is similar the UK MOT. As my car is post 95 it's meant to have the catalytic converters in place. I'm going to go for 3" turbo back exhaust and was checking out the situation regarding the cats. They don't check the condition of the cats or infact don't have to check that they're in place at all.

Everything they do is based on the exhaust fumes and this is the procedure:

Post Jan 1994 Registrations

3. For vehicles first registered on or after the 1st January 1994 raise the engine speed to 2,500 rpm or to a speed specified by the vehicle manufacturer and hold for a minimum of 30 seconds. Check the HC, CO and Lambda values.

If the exhaust emissions are not within the specified limits with the vehicle engine at normal operating temperature raise the engine speed to 2,500 rpm or to a speed specified by the vehicle manufacturer and hold for 3 minutes and note HC, CO and Lambda values.

Allow the vehicle engine to return to normal idle speed and the exhaust reading to stabilise and note the CO reading.

The cats are there to sort out the HC (hydrocarbons) is what I understand.

And finally after all that my question is can the engine be tuned to burn clean enough so the cats aren't needed. I'm thinking switchable chipset or even a pair of "test" chips that would be installed as required. ECU is socketed and will be staying Motronic.

Thanks in advance.

[JP]

Poor a bottle of cataclean (cataclear, can't remember been a while) into your fuel tank just befoe the test. It makes your engine burn hotter than normal to help clear clogged up cats. Inadvertandly it sends the emmissions testing machine up shits creak and it will pass you. It's so effective that many a year ago before the computerised system was inplace the local MOT station didn't even bother testing emmissions and just passed it if they knew you had poured a bottle into the tank.

[s2_wot]

Never heard of the stuff, sounds like a viable option. If I can bring it into the test confident of doing ok on the emmissions I'm sure then there shouldn't be any hassle.

[prj]

Nothing really to do with motronic. Make sure your lambda is okay, and you will pass if you still have cats.
If you are catless, then at least over here you can't pass legally. Your NOx will be too high.

[mcandmar]

Funny now you mention it Shane our S4 passed the NCT with a dodgy cat as one of them fell part inside. Totally forgot about it until now. On the S2 i fitted cat cypass pipes so i can keep em fresh till next time

[s2_wot]

It kinda makes designing the exhaust a bit more difficult, but I'll just change the way I was thinking so I can have cats to swap in. Dmitri's post above confirms the scenario re tuning so I'll just have to prepare for cats but I might try some of the stuff RWD19T suggested for the craic.

[JP]

Here ya go one place you can buy it from http://www.amazon.co.uk/Cataclean-Ca.../dp/B002BVXM92 long and short of it ignore all the hype how it cleans this and that. All it does is make your combustion cycle hotter burning things clean. Much the same as sitting at 7000rpm down the motorway for half an hour. Not a permanent fix but usually a good one to fiddle emmision tests so long you do it around an hour before Obviously drive the car for that hr!

[Thuppu]

So what would be the options to pass the MOT with a high HP setup?

1. Put a 4" 100cell catalytic conventer in the exhaust and leave it permanent? Does it restrict a 600+hp engine?

2. Put a normal cheap catalytic conventer with v-band flanges and switch it to a empty pipe after MOT test?

3. Do somthing to the fuel or engine managment so the emissions drops down?

4. Use E85 fuel? (Not an option for me because the nearest station is 100km away)

[prj]

2. Put a normal cheap catalytic conventer with v-band flanges and switch it to a empty pipe after MOT test?

This.

Or you can do an Y pipe and dual cats... but honestly, even without cats, you are doing hundreds of times more for the environment driving a 20 year old car, than the people buying new cars every few years.

[Thuppu]

Hmm, it would be nice to get rid of the hassle of change the cat before every MOT. How about a 5" metal core(100 cell) cat? I belive it would flow enough for 600-700hp..? Those are quite cheap on ebay.

[5cylinderman]

For the sake of a bit of effort for a few hours I can suggest a solution.
Keep the OE exhaust and modify it to fit whatever larger downpipe you plan to use. Fit the OE exhaust to the car for the NCT. Then go home and refit your proper system, after hanging you "NCT special" to your garage wall. I know a man who has been doing this for a long time with a few kit cars.

[Thuppu]

Just that is what I have been doing, but I wan't to get rid of it. You always need to be on a lifter when you change the exhaust, and the orginal exhaust with cats weight a ton. Change the exhaust before MOT and then back again right after. I hate that. Wan't a solution you can forget under the car for a few years.

Edit.

Here is the link to the catalytic converter on ebay. I think that is the best flowing cat on market..? http://www.ebay.com/itm/5-inch-Diame...fd814b&vxp=mtr

[byd1380]

I just went through MOT with my 3" system. I borrowed a 3" cat from a friend, and just made my exhaust up to suit. Simple 10 minute swap out on v-band clamps. I was running a standard RS2 chipset, the car was running very rich at idle, lots of soot in the exhaust but had no probs at all passing emissions.

Ivan

[europeanme]

2. Put a normal cheap catalytic conventer with v-band flanges and switch it to a empty pipe after MOT test?

this is my plan...along with everything else!!....

[Thuppu]

Against all recommendation, I did order the 5" 100 cell cat. It sure has great flow area and should not be restricting the flow in any way, I hope... If I had ordered a cheaper cat and a bunch of v-band clamps it would have cost me the same, and I still have to change it before and after every MOT.